In commercial applications for food heating it is desirable to provide relatively large heating compartments for containing food intended for cooking, baking, frying, thawing, etc. It is desirable that heat in such heating compartments be relatively uniformly distributed throughout the compartment for uniform or controlled heating of food products therein. It is desirable, too, that the entire appliance, i.e., a gas convection oven, be capable of being cleaned with relative ease in order to maintain high standards of cleanliness. It also is important to maintain a high degree of reliability of the equipment and facility of servicing the same.
In U.S. Pat. No. 3,605,717 there is disclosed a convection oven in which combustion of gas effects the primary heat input. In such patent there is disclosed principles of convection heating in a commercial heating appliance.
Food placed inside a convection oven is processed by moving heated air along a circulatory path directed and arranged to provide throughout the heating chamber substantially uniform temperature of a preselected and controllable level. The circulatory path is generally defined by the walls of the oven, by baffling and by food supporting devices in the food chamber. The air is moved along the circulatory path by a blower usually located adjacent the food chamber in a convection blower chamber. The blower normally is in the circulatory path.
In the past, the circulated air in convection ovens has been heated by passing the air over and around a tube-like heat exchanger such as that used in the convection oven shown in the above noted U.S. Pat. No. 3,605,717. In such convection oven, the products of combustion may enter the circulatory air path of the convection oven but this occurs at a limited outlet area of the convection blower air flow. The heat exchanger tube disclosed in such patent has several linear tube sections connected together at angles to extend generally parallel to several of the walls of the convection blower chamber so that air blown by the convection blower would flow across at least several of those linear tube sections to be heated by the hot gases flowing through the tube sections. A conical inlet baffle guides air from the heating or food chamber toward the center or inlet of the convection blower wheel, and a perimeter portion of such baffle and the oven walls guide air flow from the outlet of the convection blower wheel, as such air flows past the heat exchanger, into the heating compartment. Baffles on walls of the heating compartment and the oven walls further guide air flow toward the food or the material therein.
More recently, U.S. Pat. No. 4,484,561 disclosed a convection oven employing a novel form of heat exchanger for conducting therethrough the products of combustion from a power gas burner. The heat exchanger includes a first tubular section relatively proximate the burner and having a surface area configuration of a shape and position with respect to air flowing from the oven blower to draw air blown thereacross so as to flow across substantially the entire extent of such surface area configuration.